Queue<T>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace World2
{
    class Queue<T>
    {
        private const int CAPACITY = 5;

        private T[] entities;

        private int counter;


        public T this[int i]
        {
            get
            {
                // This indexer is very simple, and just returns or sets
                // the corresponding element from the internal array.
                return entities[i];
            }
            set
            {
                entities[i] = value;
            }
        }

        public Queue()
            : this(CAPACITY)
        { }

        public Queue(int capacity)
        {
            entities = new T[capacity];
        }

        public void Enqueue(T entity)
        {
            if (counter >= entities.Length) {
                throw new InvalidOperationException("The queue is full");
            }
            entities[counter] = entity;
            counter++;

        }

        public T Dequeue()
        {
            if (counter == 0) {
                throw new InvalidOperationException("The queue is empty");
            }
            T temp = entities[0];
            for (int i = 0; i < entities.Length - 1; i++)
            {
                entities[i] = entities[i + 1];
            }
            entities[counter - 1] = default(T);
            counter--;
            return temp;
        }

        public int GetNumberOfEntities()
        {
            return counter;
        }
    }
}